US 11,502,671 B2 · Digital pulse-width modulation (PWM) modulator with dynamically switchable code set for reduced total harmonic distortion and noise (THDN)

Abstract

A digital PWM modulator modulates a digital input signal to drive a PWM signal to a PWM DAC susceptible to introducing inter-symbol interference (ISI) in small PWM edge separation presence causing audio THDN degradation. A multi-bit quantizer switches from a first to second mode when the input signal rises above a threshold. The quantizer quantizes the input signal into a quantized output signal, each sample of which has a code selected from respective first and second quantization code sets. The second set, relative to the first set, causes the digital PWM signal to have increased edge separation to reduce the ISI at high input levels. The first set includes small magnitude codes relative to the second set to reduce quantization noise at low input levels. The threshold is sufficiently low to cause the quantized output signal to be dominated by small codes when operating in the first mode.

Claims20

Dependent claims

A digital pulse-width modulation (PWM) modulator that modulates a digital input signal to drive a digital PWM signal to a PWM digital-to-analog converter (DAC) that is susceptible to introducing inter-symbol interference (ISI) in the presence of small edge separation of the digital PWM signal causing degradation of total harmonic distortion and noise (THDN) of an audio system that comprises the digital PWM modulator and the DAC, comprising:

a state machine configured to generate a control signal based on the digital input signal;
a multi-bit quantizer switchable into at least first and second modes in response to the control signal, wherein the quantizer is configured to quantize the digital input signal into a quantized output signal, wherein each sample of the quantized output signal has a code selected from a first set of quantization codes when operating in the first mode and a code selected from a second set of quantization codes when operating in the second mode;
and
wherein the second set of quantization codes, cause the digital PWM signal to have increased edge separation relative to edge separation of the digital PWM signal caused by the first set of quantization codes to reduce the ISI.

1 more element

A method for reducing total harmonic distortion and noise (THDN) of an audio system that comprises a digital pulse-width modulation (PWM) modulator that modulates a digital input signal to drive a digital PWM signal to a PWM digital-to-analog converter (DAC) that is susceptible to introducing inter-symbol interference (ISI) in the presence of small edge separation of the digital PWM signal causing THDN degradation, comprising:

generating, by a state machine, a control signal based on the digital input signal to switch a multi-bit quantizer into at least first and second modes;
quantizing, by the quantizer, the digital input signal into a quantized output signal, wherein each sample of the quantized output signal has a code selected from first and second sets of quantization codes of the respective first and second modes;
and
wherein the second set of quantization codes, cause the digital PWM signal to have increased edge separation relative to edge separation of the digital PWM signal caused by the first set of quantization codes to reduce the ISI.

1 more element

Dependencies are inferred from the claim text.

Digital pulse-width modulation (PWM) modulator with dynamically switchable code set for reduced total harmonic distortion and noise (THDN)

Life of this patent

Digital pulse-width modulation (PWM) modulator with dynamically switchable code set for reduced total harmonic distortion and noise (THDN)

Life of this patent

Abstract

Claims20